A number of handheld and other systems for managing diabetes care currently exist. Many such systems provide for the partitioning of an extended time period, e.g., one or more days, into a number of adjacent time intervals. Within each time interval, a specific glucose target and a specific insulin sensitivity value, e.g., in units of mg/dl per international unit (IU) of insulin, may be established. It is desirable with such systems to provide for accurate determination and recommendation of additive correction insulin bolusing, regardless of when such bolusing may occur relative to adjacent time intervals, to thereby closely track and satisfy the user's insulin needs.